Optoelectronic device with heat spreader unit

ABSTRACT

A solar module includes a solar cell, a heat spreader layer disposed above the solar cell, and a cell interconnect disposed above the solar cell. From a top-down perspective, the heat spreader layer at least partially surrounds an exposed portion of the cell interconnect.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/577,616, filed Oct. 12, 2009, which claims the benefit of U.S.Provisional Application No. 61/227,024, filed Jul. 20, 2009, the entirecontents of which are hereby incorporated by reference herein.

TECHNICAL FIELD

Embodiments of the present invention are in the field of renewableenergy and, in particular, optoelectronic devices with heat spreaderunits.

BACKGROUND

Light-emitting diode (LED) and photovoltaic (PV) devices are two commontypes of optoelectronic devices. Thermal management and assembly ofoptoelectronic systems, such as systems including LED and PV devices,may be considered when evaluating such systems for fabrication anddeployment. For example, systems of devices with electrical contactsexclusively on the back side of an optoelectronic die (e.g., with anoptical interface on front side of the die) is one area ripe forimprovements in thermal management and assembly. Challenges for thefabrication and deployment of such systems include a possible need for alow resistance thermal path between the optoelectronic die and a heatsink, as well as a robust electrical isolation of operating voltages. Inorder to facilitate high volume manufacturing, design concepts andassembly techniques that are based on continuous processing may also bea consideration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a cross-sectional view of a conventional photovoltaiclaminate.

FIG. 2 illustrates a cross-sectional view of a CPV receiver with aconventional photovoltaic laminate arrangement, in accordance with anembodiment of the present invention.

FIG. 3 illustrates a cross-section of an optoelectronic device with aheat spreader unit, in accordance with an embodiment of the presentinvention.

FIG. 4 illustrates a top-down view of an optoelectronic device with aheat spreader unit, in accordance with an embodiment of the presentinvention.

FIG. 5 illustrates a cross-sectional view of a substrate prior tobonding with cells and a bypass diode, in accordance with an embodimentof the present invention.

FIG. 6 illustrates a cross-section of an optoelectronic device with aheat spreader unit, in accordance with an embodiment of the presentinvention.

FIG. 7 illustrates a top-down view of an optoelectronic device with aheat spreader unit, in accordance with an embodiment of the presentinvention.

FIG. 8 illustrates a cross-sectional view of a substrate prior tobonding with cells and a bypass diode, in accordance with an embodimentof the present invention.

FIG. 9 illustrates a top-down view representing an example of a stressrelief feature in a heat spreader layer, in accordance with anembodiment of the present invention.

FIG. 10 illustrates a cross-section of an optoelectronic device with aheat spreader unit, in accordance with an embodiment of the presentinvention.

FIG. 11 illustrates a cross-section of an optoelectronic device with aheat spreader unit, in accordance with an embodiment of the presentinvention.

FIG. 12 illustrates a cross-section of an optoelectronic device with aheat spreader unit, in accordance with an embodiment of the presentinvention.

FIG. 13 illustrates a top-down view of a stress relief feature, inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION

Optoelectronic devices with heat spreader units are described herein. Inthe following description, numerous specific details are set forth, suchas specific arrangements of heat spreader units, in order to provide athorough understanding of the present invention. It will be apparent toone skilled in the art that embodiments of the present invention may bepracticed without these specific details. In other instances, well-knownfabrication techniques, such as lamination techniques, are not describedin detail in order to not unnecessarily obscure embodiments of thepresent invention. Furthermore, it is to be understood that the variousembodiments shown in the Figures are illustrative representations andare not necessarily drawn to scale.

Disclosed herein are optoelectronic devices with heat spreader units. Inone embodiment, an optoelectronic device includes a back-contactoptoelectronic cell including a plurality of back-contact metallizationregions. One or more heat spreader units are disposed above theplurality of back-contact metallization regions. A heat sink is disposedabove the one or more heat spreader units. Also disclosed herein areoptoelectronic systems. In one embodiment, an optoelectronic systemincludes a plurality of optoelectronic devices. Each optoelectronicdevice includes a back-contact optoelectronic cell including a pluralityof back-contact metallization regions. Each optoelectronic device alsoincludes one or more heat spreader units disposed above the plurality ofback-contact metallization regions. Each optoelectronic device alsoincludes a heat sink disposed above the one or more heat spreader units.The optoelectronic system also includes a pair of cell bus bars, eachcell bus bar disposed above a different one of the pair of outerportions of each back-contact optoelectronic cell of each of theplurality of optoelectronic devices.

In accordance with an embodiment of the present invention, a thermalresistance between an optoelectronic die and an external heat sink isreduced, while a more uniform and flat surface across a high heat fluxregion of the die enclosure or package is provided. The incorporation ofa flat surface along the back side of the die enclosure may improveinterface and bond quality when attaching the enclosure to the heatsink. In one embodiment, the resulting improved thermal performanceallows optoelectronic devices to operate at lower temperatures, therebyincreasing light-to-electrical conversion efficiency and reducingdegradation and failure of device components. In addition, in oneembodiment, high volume continuous manufacturing processes are used tofabricate arrays of optoelectronic die for LED lighting applications andphotovoltaic receivers for solar concentrators. By comparison,conventional methods of photovoltaic cell array assembly may rely onbatch processing of a string of cells with sequential stacking ofcomponents that are laminated together in a final batch process. Asdiscrete components are stacked on top of each other, such as a cell andan interconnect, thickness variations may develop in the laminate. Highheat flux regions of the optoelectronic die are typically recessed fromthe regions of the stacked cell and interconnect, resulting in a poorthermal coupling to the heat sink.

Additionally, in conventional systems, the batch processing operationsmay have a low manufacturing throughput as, in accordance with anembodiment of the present invention, compared to continuous reel to reelprocessing. For example, in one embodiment, a flexible substrate isdefined and manufactured by continuous roll processing of metal foils,dielectric layers and polymer adhesive coatings. Bare optoelectronic diemay then be soldered to the leads of a substrate and encapsulatedbetween a glass cover sheet and a metal heat spreader integrated withinthe substrate at the region of highest heat flux into the die. In anembodiment, the substrate serves as an electrical interconnect to apotentially unlimited number of die and tightly couples the die thermalflux to a flat, and most proud, exterior surface of the enclosure. Inone embodiment, components of optoelectronic systems are manufactured inroll form allowing for high volume continuous processing and subsequentassembly of the optoelectronic systems. In a specific embodiment, thesubstrate provides a platform for the inclusion of integrated passivedevices, such as bypass diodes, in high volume production.

In accordance with an embodiment of the present invention, importantchallenges for the packaging of optoelectronic systems include the needfor a low resistance thermal path between a semiconductor die and a heatsink, as well as a robust electrical isolation of operating voltages.This may especially be true for arrays of high power LED lightingsystems and concentrating photovoltaic receivers. In one embodiment, inorder to meet high volume manufacturing goals, another challenge isestablishing design concepts that are compatible with continuousprocesses, such as roll feed systems. By contrast, conventionalphotovoltaic modules may be manufactured by batch processing of a smallnumber of wafers with an initial operation of soldering interconnectsbetween the wafers, providing a serially connected string of cells. Thecell string may then be placed onto a thin layer of encapsulantsupported by a relatively thick (e.g., 3 millimeters) glass superstrate.An additional layer of encapsulant and protective back sheet may beplaced on top of the cell string and the entire stack may then be batchlaminated to form a fully encapsulated system.

FIG. 1 illustrates a cross-sectional view of a conventional photovoltaiclaminate. Referring to FIG. 1, a conventional photovoltaic laminate 100includes a photovoltaic cell 102 coupled with a pair of interconnects104. Photovoltaic cell 102 and the pair of interconnects 104 is disposedin an encapsulant layer 106, above a glass superstrate 108. A back sheet110 is disposed on encapsulant layer 106.

While the system shown in FIG. 1 may be adequate for some photovoltaicmodules, the arrangement may have drawbacks when used to createconcentrating photovoltaic (CPV) receivers or high power LED lightingarrays. For example, in one embodiment, such a conventional arrangementprovides a non-flat surface on back sheet 110 with a recessed regionbetween interconnects 104 where heat flux is the highest. Additionally,the batch processing of the individual components (e.g., cellarrangement, soldering of interconnects, stacking encapsulant and backsheet) may lower manufacturing throughput.

FIG. 2 illustrates a cross-sectional view of a CPV receiver with aconventional photovoltaic laminate arrangement, in accordance with anembodiment of the present invention. Referring to FIG. 2, a CPV receiver200 with a conventional photovoltaic laminate arrangement includes aphotovoltaic cell 202 coupled with a pair of interconnects 204.Photovoltaic cell 202 and the pair of interconnects 204 is disposed inan encapsulant layer 206, above a glass superstrate 208. A heat sink 214is coupled with a back sheet 210 by an adhesive layer 212.

Referring again to FIG. 2, the overlap of photovoltaic cell 202 and thepair of interconnects 204 creates an increased gap between the high heatflux region on photovoltaic cell 202 and heat sink 214. In oneembodiment, a thermal penalty results from backfilling this region witha relatively low thermal conductivity polymer adhesive 212. Thecell-to-heat sink thermal resistance for photovoltaic cell 202 and heatsink 214 is dominated by the thermal penalty may typically representsover 50% of the total cell-to-ambient thermal resistance for aconventional cell laminate system.

In accordance with an embodiment of the present invention, the thermalpenalty described in association with FIG. 2 is mitigated or eliminated.In an embodiment, a more uniform and flat surface is provided across ahigh heat flux region of a die or cell enclosure, which may improve bondquality to a heat sink. The increased thermal performance may allowoptoelectronic devices to operate at lower temperatures, therebyincreasing light-to-electrical conversion efficiency and reducingdegradation and failure of components. In addition, in one embodiment,high volume continuous manufacturing processes is used to fabricatenearly unlimited linear arrays of devices, including passive elementssuch as diodes, for LED lighting applications and photovoltaic receiversfor solar concentrators. In an embodiment, a flexible substrate ismanufactured by continuous roll processing of metal foils, dielectriclayers and polymer adhesive coatings to define a substrate with bondpads for optoelectronic die and passive components, as well as anintegrated heat spreader. In one embodiment, thin high voltagedielectric coatings and adhesive layers are included to facilitatelamination to a glass superstrate and are also processed into thesubstrate in roll form.

In an aspect of the present invention, optoelectronic devices with heatspreader units are provided where one or more heat spreader unitsinclude a pair of cell interconnects. FIG. 3 illustrates a cross-sectionof an optoelectronic device with a heat spreader unit, in accordancewith an embodiment of the present invention.

Referring to FIG. 3, an optoelectronic device 300 includes aback-contact optoelectronic cell 302. In accordance with an embodimentof the present invention, back-contact optoelectronic cell 302 includesa plurality of back-contact metallization regions on the upper surface304 of optoelectronic cell 302. Optoelectronic device 300 also includesone or more heat spreader units 306 disposed above the plurality ofback-contact metallization regions. A heat sink 308 is disposed abovethe one or more heat spreader units 306. In accordance with anembodiment of the present invention, the one or more heat spreader units306 is part of a pair of cell interconnects, as depicted in FIG. 3. Inone embodiment, each of the pair of cell interconnects is coupled withthe plurality of back-contact metallization regions by one of a pair ofbond pads 310, as is also depicted in FIG. 3.

Referring again to FIG. 3, in accordance with an embodiment of thepresent invention, back-contact optoelectronic cell 302 includes aninner portion 302A and a pair of outer portions 302B, where each of thepair of bond pads 310 is coupled with the back-contact metallizationregions by one of a pair of cell bus bars 312. In one embodiment, eachcell bus bar 312 is disposed above a different one of the pair of outerportions 302B of back-contact optoelectronic cell 302, and a portion ofeach of the pair of cell interconnects 306 is disposed over, but not incontact with, the inner portion 302A of back-contact optoelectronic cell302, as depicted in FIG. 3.

Referring again to FIG. 3, in accordance with an embodiment of thepresent invention, the portion of each of the pair of cell interconnects306 disposed over the inner portion 302A of back-contact optoelectroniccell 302 includes a dielectric layer 314 disposed between cellinterconnect 306 and the inner portion 302A of back-contactoptoelectronic cell 302. In one embodiments, dielectric layer 314 is notin direct contact with the inner portion 302A of back-contactoptoelectronic cell 302, as is depicted in FIG. 3.

Referring again to FIG. 3, in accordance with an embodiment of thepresent invention, each of the pair of cell interconnects 306 includesan extension portion 306A that extends outside the perimeter ofback-contact optoelectronic cell 302. In one embodiment, each extensionportion 306A includes a second dielectric layer 316, as is depicted inFIG. 3. In an embodiment, back-contact optoelectronic cell 302 isdisposed above a superstrate 318, superstrate 318 proximate to a surface305 of back-contact optoelectronic cell 302 opposite the surface 304 ofback-contact optoelectronic cell 302 proximate to the one or more heatspreader units 306. In an embodiment, back-contact optoelectronic cell302 is coupled with superstrate 318 by an encapsulant material 320, andheat sink 308 is coupled with the one or more heat spreader units 306 bya thermal adhesive material 322, as depicted in FIG. 3.

In accordance with an embodiment of the present invention, a benefit ofthe arrangement described in association with FIG. 3 comes from the dualpurpose heat spreader and cell interconnect 306 which reduces thethermal resistance of the interface between back-contact optoelectroniccell 302 and heat sink 308, while providing a low electrical resistancecell interconnect 306. In an embodiment, in order to provide a highlevel of heat spreading, the cell interconnect 306 is expanded from bothedges of back-contact optoelectronic cell 302 to the center ofback-contact optoelectronic cell 302 with a small gap between to provideelectrical isolation between opposing interconnects 306. In oneembodiment, expanding the interconnect 306 to the center of back-contactoptoelectronic cell 302 aids in coupling the heat generated directlyfrom the illuminated portion of back-contact optoelectronic cell 302 tothe heat spreader units 306 and provides a low electrical resistance forback-contact optoelectronic cell 302 current generated by illumination.In an embodiment, the outer width of the interconnect and heat spreaderunit 306 that is beyond the cell edges (e.g., region 306A) is determinedbased on system geometry constraints and the thermal efficiency of theheat spreader, which is primarily a function of interconnect thickness,thermal conductivity, and distance from heat source to spreader edges.For example, in a specific embodiment, for very thin interconnect layersthe thermal efficiency of the spreader drops relatively rapidly and thuslittle thermal benefit comes from extending far beyond the cell edges.In a particular embodiment, in order to better couple the heat generatedfrom back-contact optoelectronic cell 302 into the heat spreader unit306, the dielectric layer thickness is also be minimized sincedielectric materials typically have a thermal conductivity much lowerthan a heat spreader material.

In accordance with an embodiment of the present invention, thearrangement described in FIG. 3 also enables the outer surface ofback-contact optoelectronic cell 302 enclosure to be flat, providing auniform surface for bonding heat sink 308 with an adhesive or otherbonding material. In one embodiment, from a manufacturing perspective,the use of a single metal layer to provide both heat spreading andelectrical interconnection, e.g., feature 306 of FIG. 3, reduces themanufacturing operations and facilitates continuous processes.

In an aspect of the present invention, devices such as the devicedescribed in association with FIG. 3, is includes as a substrate with aplurality of optoelectronic die and bonded bypass diodes. FIG. 4illustrates a top-down view of an optoelectronic device with a heatspreader unit, in accordance with an embodiment of the presentinvention.

Referring to FIG. 4, a system 400 includes two (or more) photovoltaiccells 402 and 404. A heat spreader unit and interconnect combinationfeature 406 is disposed above photovoltaic cells 402 and 404. In aparticular embodiment, photovoltaic cells 402 and 404 are seriallyconnected. Also depicted are a cell bond pad 408, a cell bus bar 410,and a bypass diode 412. In accordance with an embodiment of the presentinvention, the electrical connection between heat spreader unit andinterconnect combination feature 406 and cell bus bar 410 is made atcell bond pad(s) 408, utilizing a solder joint or other bondingtechnique. In an embodiment, stress relief features 414 are disposednear cell bond pads 408 to allow motion of the contact relative to theheat spreader unit and interconnect combination feature 406, in order tocreate an electrical contact to photovoltaic cells 402 and/or 404, asdescribed above in association with FIG. 3. In one embodiment, stressrelief features 414 are oriented so as to minimize electrical resistancefor current flowing between photovoltaic cells 402 and 404 by providinga shorter path and no turn angles greater than approximately 45 degrees.It is to be understood, however, that other stress relief designs couldalso be integrated. Thus, in an embodiment, at least one cellinterconnect of an optoelectronic system includes one or more stressrelief features.

In an aspect of the present invention, fabrication of a substrate isaccomplished by continuous roll processing to build-in features at highvolume and low-cost or by working with individual connectors with therequired dielectrics clad to each surface. Many different operationsequences may be contemplated to create either the continuous roll orindividual connector elements. In an embodiment, a metal layer used todefine a spreader and interconnect combination feature is manufacturedby stamping operations in order to punch out material to create stressrelief features and to down set the contact pads for enhanced interfacewith a cell. In one embodiment, narrow tie-bars are used to holdconnector strips together and are punched out at later stages in thefabrication of the substrate, or alternatively the substrate is madefrom individual connector pieces. In one embodiment, the solder or otherbonding agent used to bond the spreader and interconnect combinationfeature to the cells at the bond pads is processed onto the connectorsduring the processing of the roll or individual connector pieces.

FIG. 5 illustrates a cross-sectional view of a substrate prior tobonding with cells and a bypass diode, in accordance with an embodimentof the present invention. Referring to FIG. 5, a portion of a substratefor an optoelectronic device 500, or a plurality of devices, includes aheat spreader and cell interconnect combination feature 502, a cell bondpad 504, a cell dielectric 506, and a heat sink dielectric 508.

In conjunction with FIG. 5, it is to be understood that an optionalcarrier foil may be used to handle the substrate in roll form and canalso be introduced to the heat sink dielectric surface or the lower celldielectric surface. Additionally, an adhesive layer may be present onthe surface of the dielectric layers, in order to facilitate bonding tothe cell or encapsulant layers of the cell enclosure. A similarsubstrate could be used for large arrays of high power LEDs for lightingapplications. In accordance with an embodiment of the present invention,a flexible substrate in roll or strip form is next fed into a die bonderto attach bypass diodes and cells continuously at high volume to createcell strings of any desired length. In one embodiment, after die havebeen bonded the string of interconnected devices, the substrate can bedirectly transferred to a lamination operation in order to attach aglass superstrate.

Thus, in accordance with an embodiment of the present invention, anoptoelectronic system may be fabricated. In an embodiment, theoptoelectronic system includes a plurality of optoelectronic devices,such as the device described in association with FIG. 3. Eachoptoelectronic device includes a back-contact optoelectronic cellincluding a pair of outer portions, an inner portion, and a plurality ofback-contact metallization regions disposed on the inner portion. One ormore heat spreader units is disposed above the plurality of back-contactmetallization regions. A heat sink is disposed above the one or moreheat spreader units. The optoelectronic system also includes a pair ofcell bus bars, each cell bus bar disposed above a different one of thepair of outer portions of each back-contact optoelectronic cell of eachof the plurality of optoelectronic devices.

In an embodiment, the one or more heat spreader units of eachback-contact optoelectronic cell includes a pair of cell interconnects,each of the pair of cell interconnects coupled with the plurality ofback-contact metallization regions by one of a pair of bond pads. In oneembodiment, each of the pair of bond pads of each back-contactoptoelectronic cell is coupled with the back-contact metallizationregions by one of the pair of cell bus bars, and a portion of each ofthe pair of cell interconnects of each back-contact optoelectronic cellis disposed over, but not in contact with, the inner portion of theback-contact optoelectronic cell. In one embodiment, for eachback-contact optoelectronic cell, the portion of each of the pair ofcell interconnects disposed over the inner portion of the back-contactoptoelectronic cell includes a dielectric layer disposed between thecell interconnect and the inner portion of the back-contactoptoelectronic cell, but not in contact with the inner portion of theback-contact optoelectronic cell. In a particular embodiment, thedielectric layer is not in direct contact with the inner portion of theback-contact optoelectronic cell.

In an embodiment, for each back-contact optoelectronic cell, each of thepair of cell interconnects includes an extension portion that extendsoutside the perimeter of the back-contact optoelectronic cell, and eachextension portion includes a second dielectric layer. In one embodiment,for each back-contact optoelectronic cell, the back-contactoptoelectronic cell is disposed above a superstrate, the superstrateproximate to a surface of the back-contact optoelectronic cell oppositethe surface of the back-contact optoelectronic cell proximate to the oneor more heat spreader units, the back-contact optoelectronic cell iscoupled with the superstrate by an encapsulant material, and the heatsink is coupled with the one or more heat spreader units by a thermaladhesive material.

In an aspect of the present invention, optoelectronic devices with heatspreader units are provided where one or more heat spreader units iselectrically isolated from a plurality of back-contact metallizationregions. FIG. 6 illustrates a cross-section of an optoelectronic devicewith a heat spreader unit, in accordance with an embodiment of thepresent invention.

Referring to FIG. 6, an optoelectronic device 600 includes aback-contact optoelectronic cell 602. In accordance with an embodimentof the present invention, back-contact optoelectronic cell 602 includesa plurality of back-contact metallization regions on the upper surface604 of optoelectronic cell 602. Optoelectronic device 600 also includesone or more heat spreader units 606 disposed above the plurality ofback-contact metallization regions. A heat sink 608 is disposed abovethe one or more heat spreader units 606. In accordance with anembodiment of the present invention, the one or more heat spreader units606 is electrically isolated from the plurality of back-contactmetallization regions, as depicted in FIG. 6 through the use ofdielectric layer 614. In one embodiment, a pair of cell interconnects699 is coupled with the plurality of back-contact metallization regionsby one of a pair of bond pads 610, as depicted in FIG. 6. In anembodiment, each of the pair of bond pads 610 is coupled with theback-contact metallization regions by one of a pair of cell bus bars(not shown).

Referring again to FIG. 6, in accordance with an embodiment of thepresent invention, back-contact optoelectronic cell 602 includes aninner portion 602A and a pair of outer portions 602B, and the one ormore heat spreader units 606 is disposed over the inner portion 602A ofback-contact optoelectronic cell 602. In one embodiment, back-contactoptoelectronic cell 602 is disposed above a superstrate 618, superstrate618 proximate to a surface 605 of back-contact optoelectronic cell 602opposite the surface 604 of back-contact optoelectronic cell 602proximate to the one or more heat spreader units 606, as depicted inFIG. 6. In an embodiment, back-contact optoelectronic cell 602 iscoupled with superstrate 618 by an encapsulant material 620, and heatsink 608 is coupled with the one or more heat spreader units 606 by athermal adhesive material 622. In accordance with an embodiment of thepresent invention, a dielectric layer 614 is disposed between the one ormore heat spreader units 606 and back-contact optoelectronic cell 602,as is depicted in FIG. 6.

In accordance with an embodiment of the present invention, a benefit ofthe arrangement described in association with FIG. 6 comes from theclose thermal coupling of back-contact optoelectronic cell 602 to heatspreader 606 and heat sink 608. In an embodiment, this arrangement ismade possible by the inclusion of through holes in the spreader anddielectric layer that accommodate the cell interconnects. In oneembodiment, heat spreader 606 is composed of a metal layer withsignificantly higher thermal conductivity than adhesives and encapsulantmaterials and further reduces the thermal resistance betweenback-contact optoelectronic cell 602 and heat sink 608.

In an aspect of the present invention, the arrangement of FIG. 6 enablesthe outer surface of the enclosure of back-contact optoelectronic cell602 to be flat, providing a uniform surface for bonding a heat sink withan adhesive or other bonding material. FIG. 7 illustrates a top-downview of an optoelectronic device with a heat spreader unit, inaccordance with an embodiment of the present invention.

Referring to FIG. 7, a system 700 includes two (or more) photovoltaiccells 702 and 704. A cell interconnect 706 is disposed abovephotovoltaic cells 702 and 704. In a particular embodiment, photovoltaiccells 702 and 704 are serially connected. Also depicted is a bypassdiode 712. In accordance with an embodiment of the present invention, atleast one cell interconnect of the optoelectronic system includes one ormore stress relief features.

In accordance with an embodiment of the present invention, fabricationof a substrate is accomplished via continuous roll processing to buildin features at high volume and low-cost. In one embodiment, the processbegins by applying a dielectric coating to a continuous strip of metalused to define a heat spreader. After the dielectric is coated, throughholes are punched into the spreader to allow space for cellinterconnects and passive components such as the bypass diode. Anadditional thin adhesive layer, e.g. EVA, can also be applied to thedielectric surface to facilitate bonding to the cell and interconnectlayer. In an embodiment, the interconnect layer is then added to theroll containing the dielectric and heat spreader to define a bi-metallicsystem with isolating dielectric layer that is ready to bond cells andother components. The interconnect layer may be processed withpre-plated soldering pads or other features to allow soldering orbonding of semiconductor die. In alternative embodiments of thesubstrate fabrication process, the substrate may be defined by buildingup the bi-metallic layers from both sides of dielectric core or bybuilding up from the lower interconnect layer. In an embodiment, apossible advantage of such fabrication processes over conventionaltechniques is the high volume roll processing of the interconnects, heatspreader and dielectric into a single component rather than integratingthese components individually into a batch process.

FIG. 8 illustrates a cross-sectional view of a substrate prior tobonding with cells and a bypass diode, in accordance with an embodimentof the present invention. Referring to FIG. 8, a portion of a substratefor an optoelectronic device 800, or a plurality of devices, includes aheat spreader 802, a cell bond pad 804, a dielectric layer 806, a pairof cell interconnects 808, and an adhesive layer 810. In accordance withan embodiment of the present invention, heat spreader 802 iselectrically isolated from the pair of cell interconnects 808, as isdepicted in FIG. 8. In accordance with an alternative embodiment of thepresent invention, dielectric layer 806 and adhesive layer, and possiblyan encapsulant layer, are actually a single material layer with multiplefunctionalities.

In conjunction with the description of FIG. 8, a flexible substrate inroll form may then be fed into a die bonder to attach bypass diodes andcells continuously at high volume to create cell strings of any desiredlength. In an embodiment, after die have been bonded, the string ofinterconnected devices can be directly transferred to a laminationoperation to attach a glass superstrate. It is noted that in anembodiment, stress relief features can be added to the heat spreader andcell interconnect layers to reduce stresses that develop from hightemperature bonding and laminating operations. An example of a stressrelief feature 902 in a heat spreader layer 904 is shown in FIG. 9, inaccordance with an embodiment of the present invention. In anembodiment, temporary structural tie-bars can also be integrated intothe interconnect and heat spreader layers that are punched out in alater stage of processing.

Thus, in accordance with an embodiment of the present invention, anoptoelectronic system may be fabricated. In an embodiment, theoptoelectronic system includes a plurality of optoelectronic devices,such as the device described in association with FIG. 6. Eachoptoelectronic device includes a back-contact optoelectronic cellincluding a pair of outer portions, an inner portion, and a plurality ofback-contact metallization regions disposed on the inner portion. One ormore heat spreader units is disposed above the plurality of back-contactmetallization regions. A heat sink is disposed above the one or moreheat spreader units. The optoelectronic system also includes a pair ofcell bus bars, each cell bus bar disposed above a different one of thepair of outer portions of each back-contact optoelectronic cell of eachof the plurality of optoelectronic devices.

In an embodiment, for each back-contact optoelectronic cell, the one ormore heat spreader units is electrically isolated from the plurality ofback-contact metallization regions. In one embodiment, for eachback-contact optoelectronic cell, the back-contact optoelectronic cellincludes an inner portion and a pair of outer portions, and the one ormore heat spreader units is disposed over the inner portion of theback-contact optoelectronic cell. In one embodiment, for eachback-contact optoelectronic cell, the back-contact optoelectronic cellis disposed above a superstrate, the superstrate proximate to a surfaceof the back-contact optoelectronic cell opposite the surface of theback-contact optoelectronic cell proximate to the one or more heatspreader units, the back-contact optoelectronic cell is coupled with thesuperstrate by an encapsulant material, and the heat sink is coupledwith the one or more heat spreader units by a thermal adhesive material.

In another aspect of the present invention, different configuration of aheat sink may be contemplated. FIG. 10 illustrates a cross-section of anoptoelectronic device with a heat spreader unit, in accordance with anembodiment of the present invention.

Referring to FIG. 10, an optoelectronic device 1000 includes aback-contact optoelectronic cell 1002. In accordance with an embodimentof the present invention, back-contact optoelectronic cell 1002 includesa plurality of back-contact metallization regions on the upper surface1004 of optoelectronic cell 1002. Optoelectronic device 1000 alsoincludes one or more heat spreader units 1006 disposed above theplurality of back-contact metallization regions. A folded fin heat sink1008 is disposed above the one or more heat spreader units 1006. Inaccordance with an embodiment of the present invention, the one or moreheat spreader units 1006 is part of a pair of cell interconnects, asdepicted in FIG. 10. In one embodiment, each of the pair of cellinterconnects is coupled with the plurality of back-contactmetallization regions by one of a pair of bond pads 1010, as is alsodepicted in FIG. 10.

FIG. 11 illustrates a cross-section of an optoelectronic device with aheat spreader unit, in accordance with an embodiment of the presentinvention. Referring to FIG. 11, an optoelectronic device 1100 includesa back-contact optoelectronic cell 1102. In accordance with anembodiment of the present invention, back-contact optoelectronic cell1102 includes a plurality of back-contact metallization regions on theupper surface 1104 of optoelectronic cell 1102. Optoelectronic device1100 also includes one or more heat spreader units 1106 disposed abovethe plurality of back-contact metallization regions. A folded fin heatsink 1108 is disposed above the one or more heat spreader units 1106. Inaccordance with an embodiment of the present invention, the one or moreheat spreader units 1106 is electrically isolated from the plurality ofback-contact metallization regions, as depicted in FIG. 1. In oneembodiment, a pair of cell interconnects 1199 is coupled with theplurality of back-contact metallization regions by one of a pair of bondpads 1110, as depicted in FIG. 11. In an embodiment, each of the pair ofbond pads 1110 is coupled with the back-contact metallization regions byone of a pair of cell bus bars (not shown). In an embodiment,optoelectronic device 1100 includes a cell dielectric layer 1112 and aspreader through-hole 1114. In an embodiment, optoelectronic device 1100includes a heat sink dielectric layer 1116. In one embodiment, heat sinkdielectric layer 1116 adds additional insulation protection andpotentially a “cap” for spreader through-hole 1114 if added after theone or more heat spreader units 1106 and spreader through-hole 1114 arepunched.

In an aspect of the present invention, multiple levels of heat spreaderunits may be included above a cell. For example, FIG. 12 illustrates across-section of an optoelectronic device with a heat spreader unit, inaccordance with an embodiment of the present invention.

Referring to FIG. 12, an optoelectronic device 1200 includes aback-contact optoelectronic cell 1202. In accordance with an embodimentof the present invention, back-contact optoelectronic cell 1202 includesa plurality of back-contact metallization regions on the upper surface1204 of optoelectronic cell 1202. Optoelectronic device 1200 alsoincludes one or more heat spreader units 1206 disposed in a first layerabove the plurality of back-contact metallization regions. In accordancewith an embodiment of the present invention, the one or more heatspreader units 1206 is electrically isolated from the plurality ofback-contact metallization regions, as depicted in FIG. 12. In oneembodiment, a pair of cell interconnects 1299 is coupled with theplurality of back-contact metallization regions by one of a pair of bondpads 1210, as depicted in FIG. 12. In an embodiment, each of the pair ofbond pads 1210 is coupled with the back-contact metallization regions byone of a pair of cell bus bars (not shown). In accordance with anembodiment of the present invention, optoelectronic device 1200 furtherincludes an upper heat spreader unit 1240 disposed above the one or moreheat spreader units 1206, and separated from the one or more heatspreader units by an upper dielectric layer 1242. In one embodiment, anoptoelectronic system includes a plurality of back-contactoptoelectronic cells, each back-contact optoelectronic cell furtherincluding an upper heat spreader unit, such as upper heat spreader unit1240, disposed above one or more heat spreader units, and separated fromthe one or more heat spreader units by an upper dielectric layer, suchas upper dielectric layer 1242. In an embodiment, optoelectronic device1200 also includes a cell dielectric layer 1250. In an embodiment,optoelectronic device 1200 also includes a heat sink 1208 disposed aboveupper heat spreader unit 1240, as depicted in FIG. 12.

It is to be understood that the discussion of stress relief featuresherein is not limited to the features depicted and described above. Asanother example, FIG. 13 illustrates a top-down view of a stress relieffeature, in accordance with an embodiment of the present invention.Referring to FIG. 13, an optoelectronic system 1300 includes one or morephotovoltaic cells 1302, a cell bond pad 1304, a bypass diode 1306, acell bus bar 1308, and a stress relief feature 1310 which is alsomagnified in FIG. 13.

Thus, optoelectronic devices with heat spreader units have beendisclosed. In accordance with an embodiment of the present invention, anoptoelectronic device includes a back-contact optoelectronic cellincluding a plurality of back-contact metallization regions. Theoptoelectronic device also includes one or more heat spreader unitsdisposed above the plurality of back-contact metallization regions. Theoptoelectronic device also includes a heat sink disposed above the oneor more heat spreader units. In one embodiment, the one or more heatspreader units includes a pair of cell interconnects, each of the pairof cell interconnects coupled with the plurality of back-contactmetallization regions by one of a pair of bond pads. In anotherembodiment, the one or more heat spreader units is electrically isolatedfrom the plurality of back-contact metallization regions.

1. A solar module, comprising: a solar cell; a heat spreader layerdisposed above the solar cell; and a cell interconnect disposed abovethe solar cell, wherein, from a top-down perspective, the heat spreaderlayer at least partially surrounds an exposed portion of the cellinterconnect.
 2. The solar module of claim 1, wherein the exposedportion of the cell interconnect comprises a portion of a tab of thecell interconnect.
 3. The solar module of claim 1, wherein, from thetop-down perspective, the heat spreader layer is disposed above the cellinterconnect, and wherein the heat spreader layer completely surroundsthe exposed portion of the cell interconnect.
 4. The solar module ofclaim 3, wherein the exposed portion of the cell interconnect comprisesa tab of the cell interconnect.
 5. The solar module of claim 1, whereinthe solar cell comprises a plurality of contact metallization regions ona surface of the solar cell proximate to the heat spreader layer, andwherein the heat spreader layer is electrically isolated from theplurality of contact metallization regions.
 6. The solar module of claim1, wherein the solar cell comprises an inner portion and a pair of outerportions, and wherein the heat spreader layer is disposed above and overonly the inner portion.
 7. The solar module of claim 1, wherein thesolar cell comprises an inner portion and a pair of outer portions, andwherein the heat spreader layer is disposed above and over both theinner portion and the outer portions.
 8. The solar module of claim 1,wherein a portion of the heat spreader layer that at least partiallysurrounds the exposed portion of the cell interconnect is astress-relief feature.
 9. The solar module of claim 1, wherein the solarcell is a back-contact solar cell.
 10. A solar module, comprising: aplurality of solar cells; a heat spreader layer disposed above theplurality of solar cells; and a plurality of cell interconnects, eachcoupling a pair of the solar cells, wherein, from a top-downperspective, the heat spreader layer at least partially surroundsexposed portions of one or more of the cell interconnects.
 11. The solarmodule of claim 10, wherein the exposed portions of the one or more cellinterconnects comprises a portion of a tab of the one or more cellinterconnects.
 12. The solar module of claim 10, wherein, from thetop-down perspective, the heat spreader layer is disposed above theplurality of cell interconnects, and wherein the heat spreader layercompletely surrounds the exposed portions of the one or more cellinterconnects.
 13. The solar module of claim 12, wherein the exposedportions of the one or more cell interconnects each comprises a tab ofthe one or more cell interconnects.
 14. The solar module of claim 10,wherein each of the solar cells comprises a plurality of contactmetallization regions on a surface of the solar cell proximate to theheat spreader layer, and wherein the heat spreader layer is electricallyisolated from the plurality of contact metallization regions.
 15. Thesolar module of claim 10, wherein each of the solar cells comprises aninner portion and a pair of outer portions, and wherein the heatspreader layer is disposed above and over only the inner portion. 16.The solar module of claim 10, wherein each of the solar cells comprisesan inner portion and a pair of outer portions, and wherein the heatspreader layer is disposed above and over both the inner portion and theouter portions.
 17. The solar module of claim 10, wherein portions ofthe heat spreader layer that at least partially surround the exposedportions of the one or more cell interconnects are stress-relieffeatures.
 18. The solar module of claim 10, wherein each of the solarcells is a back-contact solar cell.